1. Field of the Invention
The present invention relates generally to a fluid-actuated hub clutch for use in rotary mechanical transmission and drive systems. More particularly, the invention relates to a clutch device which can be interposed between driving and driven elements, such as on the low-speed side of a gear reducer, and which can be actuated, controlled and monitored via structures provided in a compact, self-contained package.
2. Description of the Related Art
A wide range of applications exist in industry for rotary power transmission devices which can be selectively coupled and uncoupled to a driven load. Power transmitted through such systems originates in a prime mover, such as an electric motor or an internal combustion engine. Power is output from the prime mover via a rotating shaft or hub which is, in turn, connected to a driven load. In many applications the torques and speeds output by the prime mover do not consistently match the requirements of the load, requiring a speed reducer between the prime mover and the driven load. Reducers of this type, typically including one or more stages of intermeshing gears, not only serve to adapt the prime mover speed, but amplify the torque output by the prime mover.
In addition to the prime mover and interfacing hardware for linking the prime mover to a driven load, many power transmission systems require the ability to selectively connect and disconnect the prime mover and the load. Various clutch devices have been proposed and are currently in use for this purpose. Depending upon the load requirements (i.e., torques and speeds passed through the clutch), such clutches may be actuated electrically, by pressurized fluid, by centrifugal structures, and so forth. For large or high inertia loads, such as those found in many industrial, material handling, mining, and similar applications, fluid clutches offer significant advantages of enhanced controllability and efficiency.
Rotary power transmission systems employed in many xe2x80x9cheavy dutyxe2x80x9d applications must often respond to additional needs over and above those of simple torque and speed transmission. In particular, where very large loads are to be driven, inertial factors require that the power transmission systems be adapted to start and stop the loads progressively or in various controlled manners. To accommodate such needs, integrated gear reducers and clutch systems have been developed which offer both gear reduction and controllable fluid clutch operation in a single package. One integrated power transmission system of this type is commercially available from Rockwell Automation Power Systems, Dodge CST Division of Seattle, Washington. Systems of this type offer the significant advantage of permitting controlled starting and stopping of high inertial loads. Where desired, they may also be instrumented to provide for monitoring of loads, temperatures, speeds and so forth. Such integrated power transmission systems are particularly well suited to low-speed, high-inertia applications, such as conveyor drives in mining, timber, utility and other industries, as well as to other types of rotary drives such as trommel drives, ball mill drives, and so forth.
While integrated gear reducer and fluid clutch systems are suitable for many applications, in certain situations it would be useful to allow controllable fluid clutches to be installed independently of gear reducers, such as between the gear reducers and driven loads. In particular, there exists a need for a controllable fluid clutch system which can be interposed between a gear reducer coupled to a prime mover, and a driven load, in a separate package from the gear reducer itself. Such clutches would both permnit greater flexibility in the selection of a gear reducer, as well as offer the possibility to retrofit existing systems with the improved clutch, while interfacing the retrofitted clutch with gear reducers and other power transmission hardware already in place.
Existing stand-alone fluid clutch systems are not well suited to satisfying these needs. For example, in one known system, a fluid clutch is interposed on a high-speed side of a gear reducer, and interface with the output shaft of a prime mover, and the input shaft of the gear reducer. The clutch package generally requires alignment of the prime mover shaft and the gear box shaft for proper operation. Moreover, provision of the clutch on the input side of the gear reducer limits the controllability of the power transmission system by interposing the multiple elements of the gear reducer between the controlled clutch and the ultimate load.
Other clutch systems have been proposed and are currently in use in which fluid used to actuate the clutch is channeled through a driven shaft. The shaft may be an integral part of downstream power transmission equipment, such as a belt pulley shaft. The actuating fluid is channeled from the shaft to a piston assembly within the fluid clutch which serves to engage and disengage clutch plates. Such structures are not well suited, however, for use with non-channeled shafts, severely limiting their utility in new and retrofit applications in which associated equipment is supplied with conventional (i.e., non-channeled shafting). Accordingly, there is a need for an improved controllable fluid clutch system in which actuating fluid is not required to be channeled through shafting of associated equipment.
In addition to the foregoing issues with clutched power transmission systems, problems often arise in the mating and mounting of the upstream and downstream power transmission components on either side of a clutch. In certain system designs, the clutch. may even serve to support driving or driven components on an input or output shaft. In such cases, an extremely reliable and solid connection must be made between the supporting shaft and the clutch. In many cases, the mating elements are specifically machined to fit one another, with little interoperability offered between components of other sizes or configurations. There is also, therefore, a present need for an improved system for coupling a hub, such as a clutch hub, to an input or output shaft. There is a particular need for a system which can provide a sufficiently rigid and reliable connection to allow the clutch, and other components where desired, to be supported on the coupled shaft during operation.
The invention provides a controllable fluid-actuated clutch designed to respond to these needs. The clutch is formed with an inner hub assembly which may serve as either the input to the clutch or the output from the clutch, depending upon the application. The hub assembly is designed to receive conventional shafting, without the need to direct actuating fluid through the shafting. A housing surrounds the inner hub and is designed to be coupled to another transmission element, either an input element or an output element, depending upon the application of the clutch. A clutch plate stack is provided between the hub assembly and the housing assembly. The clutch plates of the stack can be selectively engaged by fluid pressure to cause the housing and hub to rotate together, thereby transmitting power through the clutch. The clutch may also include features on the housing to permit it to be interfaced with specific types of drives, such as external gears, trommel drives and the like. The clutch may also be instrumented to provide monitoring and feedback signals representative of operational parameters of the mechanical and fluid components. The resulting structure is both compact and adaptable to both new and retrofit applications.
The clutch may serve as a coupling element between the driving and driven components. In a preferred configuration, an outer housing rotates with the first of the components, such as an output shaft from a gear box, while the hub rotates with an output shaft, such as a pulley shaft, or other driven load. A stationary, or static, piston housing is coupled to a manifold for routing fluids into and out of the clutch. The piston housing includes passages for actuating fluid used to engage and disengage the clutch plate stack, thereby causing engagement and disengagement of the outer housing with the hub. Additional passages in the manifold are provided for receiving and transmitting cooling fluid to internal regions of the clutch. Bearing assemblies between the outer housing, the piston housing, and the hub, support the housings and hub effectively with one another, providing adequate mechanical support for hanging a load or a prime mover supported on the input or output shaft.
In a presently preferred configuration, the clutch hub may be supported on shafts of various sizes via a tapered bushing and bushing adapter arrangement. The tapered bushing extends between the hub and the support shaft, with a support adapter being provided between the tapered bushing and the shaft for applications where the shaft dimensions do not match those of the inner dimensions of the tapered bushing. The tapered bushing may be installed with the adapter in a hydraulic coupling technique, so as to provide an extremely rigid and reliable connection of the hub and shaft with one another. A single size of clutch or hub may thus be employed with variously sized and configured shafts.